Retired cycling champ Lance Armstrong filed a federal lawsuit on
Monday seeking to stop the U.S. Anti-Doping Agency from
proceeding with a case that charges him with taking
performance-enhancing drugs.

Armstrong faces a Saturday deadline to either challenge the
charges or accept sanctions that could strip him of his seven
Tour de France titles and ban him from the sport for life if he
is found guilty. His attorneys also sought a temporary
restraining order to halt the process.

The USADA is a quasi-governmental agency created by Congress in
2000 and charges would be considered by its own arbitration
process. Any penalties would be binding within the sport, but
federal courts have the power to overrule the agency.

Lawyers for Armstrong contend that the USADA gathered evidence by
threatening to ruin the careers of fellow cyclists who have
agreed to testify against him. Lawyers for Armstrong also argue
that the agency's rules violate Armstrong's right to a fair trial
and that it lacks proper jurisdiction to charge him.

The legal action, filed in Armstrong's Austin, Texas, hometown,
claims the agency's investigation is causing "irreparable" damage
to the champion cyclist, who won seven straight Tour de France
championships between 1999 and 2005.

In a statement issued Monday, the USADA said Armstrong's lawsuit
is "without merit" and that USADA rules "provide full
constitutional due process… designed to protect the rights of
clean athletes and the integrity of the sport."

Accusations of doping have dogged Armstrong since he ascended to
the top of the cycling world after overcoming cancer. In
February, the U.S. Justice Department dropped an investigation
centered on whether Armstrong and his teammates cheated the
sponsor of their bike racing team, the U.S. Postal Service, with
a secret doping program.

Last month, the USADA formally charged Armstrong with doping and
taking part in a conspiracy with members of his championship
teams. Five other cyclists have been accused of conspiring with
Armstrong over the course of 14 years to hide doping activity.

The agency said in a letter to Armstrong that it has blood
samples from 2009 and 2010 that are "fully consistent" with
doping. In the letter, which was published in the Washington Post, the agency said it also
has at least 10 former teammates and colleagues of Armstrong that
will testify that he used doping drugs during races from 1999 to
2005.

Armstrong's attorneys contend that he has "passed every drug test
ever administered to him in his career - a total of 500 to 600
tests... more drug tests than any athlete in history."

They say the International Cycling Union has proper jurisdiction
in the case.

(Reporting By Chris Francescani in New York; Editing by Paul
Thomasch and Cynthia Osterman)